View Compilation Error

0_0_18541537_4441.cpp: In function 'int bfs(int)':
0_0_18541537_4441.cpp:40:33: error: 'memset' was not declared in this scope
  memset(level, -1, sizeof(level));
                                 ^
0_0_18541537_4441.cpp: In function 'void build()':
0_0_18541537_4441.cpp:79:31: error: 'memset' was not declared in this scope
  memset(head, -1, sizeof(head));
                               ^